The invention is directed to a more efficient approach for implementing floorplanning, layout, placement, and routing of integrated circuit designs.
A semiconductor integrated circuit (IC) has a large number of electronic components, such as transistors, logic gates, diodes, wires, etc., that are fabricated by forming layers of different materials and of different geometric shapes on various regions of a silicon wafer.
Many phases of physical design may be performed with computer aided design (CAD) tools or electronic design automation (EDA) systems. To design an integrated circuit, a designer first creates high level behavior descriptions of the IC device using a high-level hardware design language. An EDA system typically receives the high level behavior descriptions of the IC device and translates this high-level design language into netlists of various levels of abstraction using a computer synthesis process. A netlist describes interconnections of nodes and components on the chip and includes information of circuit primitives such as transistors and diodes, their sizes and interconnections, for example.
An integrated circuit designer may uses a set of layout EDA application programs to create a physical integrated circuit design layout from a logical circuit design. The layout EDA application uses geometric shapes of different materials to create the various electrical components on an integrated circuit and to represent electronic and circuit IC components as geometric objects with varying shapes and sizes. After an integrated circuit designer has created an initial integrated circuit layout, the integrated circuit designer then verifies and optimizes the integrated circuit layout using a set of EDA testing and analysis tools. Verification may include, for example, design rule checking to verify compliance with rules established for various IC parameters.
Typically, geometric information about the placement of the nodes and components onto the chip is determined by a placement process and a routing process. The placement process is a process for placing electronic components or circuit blocks on the chip and the routing process is the process for creating interconnections between the blocks and components according to the specified netlist.
Based upon this geometric information, photomasks are created for lithographic manufacturing of the electronic product. A photomask, or more simply a “mask,” provides the master image of one layer of a given integrated chip's physical geometries. A typical photolithography system projects UV light energy on to and through the mask in order to transmit the mask pattern in reduced size to the wafer surface, where it interacts with a photosensitive coating on the wafer.
Other processes may also occur during the process of manufacturing an intenerated circuit. For example, etching, Electroplated copper deposition (ECD), and chemical mechanical polishing (CMP) may be used to form interconnects for the IC. The lithographic patterns define the dimensions of the circuitry that is transferred to a silicon wafer, with the patterns subsequently used with the etch process to physically etch the features into the wafer surface or other thin films deposited on the wafer surface. Etch equipment includes mechanisms to selectively remove materials (e.g. oxide) from a wafer surface or thin films on the wafer surface patterned with lithography equipment. ECD is a process step in a copper damascene flow that is used to deposit copper material within the interconnect structures.
However, significant variations may arise during the process of manufacturing the IC. For example, lithography mask creation and printing assume that projection is done on a film, within a predetermined depth of focus range. However pattern dependencies between the process by which the ICs are fabricated and the pattern that is being created often cause processed films to have significant variation in thickness across a surface, resulting in variation in feature dimensions (e.g. line widths) of ICs that are patterned using the mask.
Variations in feature density, widths, and heights may also occur during the CMP and plating processes. Variations based upon CMP and plating process are often caused by oxide loss, dishing, erosion, or other copper losses. For ECD, the goal is to completely fill an etched trench region in a void-free manner while minimizing a variation in the deposited copper thickness and minimizing a variation in surface topography. There may exist pattern-dependencies in ECD that result in plated surface variation. Film thickness variation in CMP processes can be separated into various components: lot-to-lot, wafer-to-wafer, wafer-level, and die-level. Often, the most significant component is the pattern dependent die-level component. Die-level film thickness variation is often due to differences in layout patterns on the chip. For example, in the CMP process, differences in the underlying metal pattern result in large long-range variation in the post CMP film thickness, even though a locally planar surface topography is achieved.
As successive non-conformal layers are deposited and polished, the variation becomes worse. The variations may lead to numerous problems and flaws in a manufactured IC, such as timing failures, decreased performance, and increased power consumption. As just one example, because interconnect lines and connections on higher layers carry power to portions of the chip, the variations can increase the sheet resistance and thus affect the power effectiveness of the chip.
Thickness variation is one example of a type of topological variation that may occur based upon the manufacturing processes for an integrated circuit. Thickness variations may cause numerous problems for the structures in the IC, such as routing structures. For example, thickness issues may result in resistance based effects for the IC interconnects, which causes higher delays and timing problems for the chip. In addition, polishing effects may affect thickness resulting in capacitance problems for the manufactured chip. Thickness variations may create polishing problems, such as copper pooling problems, which actually result in short circuits within the chip.
Conventional EDA systems fail to take manufacturing variations into account when performing layout, floorplanning, placement, and routing functions. For example, conventional routers fail to take thickness variations into account when performing routing functions. This is quite problematic since, as noted above, thickness variations could cause operational or yield problems with the manufactured IC chip.
Therefore, there is a need for an improved method and system for implementing IC designs that limits the amount of resources consumed by DRC (design rule checking) processing.
The present invention is a method, system, and computer program product for model-based method for layout, floorplanning, placement and routing. Models are used to guide the placement and routing of polygons on the IC layout. In effect, the parameters that are used for placement and routing are guided by the model data so that the layout can be formed with a high degree of manufacturability from the outset. The present invention overcomes the limitations of conventional by considering manufacturing-based variations when implementing or modifying a layout, floorplan, placement, or route. With regard to routing, the variation analysis, e.g., thickness variation analysis, is used to either optimize routes or perform verification upon routes.